Hennessy was given a fake visa to fly to Tripoli, but on arrival he was arrested by a militia and taken to a detention centre near the airport.

"There were daily abuses," he said. "If people make noise, or rush for food, you get beaten."

The weapon of choice for the guards was a water pipe.

Some of his fellow detainees outlined other hazards on the migrant trail through Libya - being bought and sold by militias, used as slave labour, and forced to bribe guards to be released from detention centres.

Dreaming of being deported

Each man received a small bread roll, some butter, and a single cup of watery juice.

Image caption
Three-month-old Sola has been in detention for most of his short life

The detainees wanted us to witness this, as did the officials in charge. They say they have run out of money to pay their suppliers and are now relying on donations.

Those behind bars here are effectively prisoners, who don't know their sentence. They can be held indefinitely - with no legal process. Their only hope of release is to be sent back to their home country.

Three-month-old Sola has been in detention for most of his short life.

We found him in the women's section, sleeping peacefully on a faded mattress.

His young mother, Wasila Alasanne, tried to take him across the seas to Italy when he was just four weeks old.

"Our boat broke and the police arrested us on the water," she said.

"Since then we have been in five prisons. We don't have enough food. We don't have the right to call our parents. They don't know if I am alive or dead. My baby and I are suffering."

Wasila's husband is being held in a different detention centre.

She has no idea when they will be reunited, or when they will free.

Her home country, Togo, has no ambassador in Libya.

Now she can only dream of deportation, as she used to dream of Europe.

A note on terminology: The BBC uses the term migrant to refer to all people on the move who have yet to complete the legal process of claiming asylum. This group includes people fleeing war-torn countries such as Syria, who are likely to be granted refugee status, as well as people who are seeking jobs and better lives, who governments are likely to rule are economic migrants.